In recent years, in the production of semiconductor elements and liquid crystal display elements, advances in lithography techniques have lead to rapid progress in the field of miniaturization of a pattern. Typically, these miniaturization techniques involve shortening the wavelength of the exposure light source. Conventionally, ultraviolet radiation typified by g-line and i-line radiation has been used, but nowadays, mass production of semiconductor elements using KrF excimer lasers and ArF excimer lasers has commenced. Furthermore, investigations are also being conducted into the use of radiation with even shorter wavelengths than these excimer lasers, including F2 excimer lasers, electron beams, extreme ultraviolet radiation, and X-rays.
One example of a known resist material that satisfies the high resolution properties necessary for reproducing patterns of minute dimensions is a chemically amplified resist composition, which includes a base resin that undergoes a change in alkali solubility under the action of acid, and an acid generator that generates acid on exposure. These chemically amplified resist compositions include negative compositions that contain an alkali-soluble resin, an acid generator and a cross-linking agent, and positive compositions that contain a resin that exhibits increased alkali solubility under the action of acid, and an acid generator.
For example, resins (acrylic resins) containing structural units derived from (meth)acrylic acid are widely used as the base resin for resists used within ArF excimer laser lithography as they offer excellent transparency in the vicinity of 193 nm (see patent reference 1).
[Patent Reference 1]
Japanese Unexamined Patent Application, First Publication No. 2003-167347